The harmonic distortion at the Point of Common Coupling on the electrical grid has to be within the limits specified e.g. by a grid code specification. The harmonic distortion on the grid is caused due to variations of harmonic grid impedance due to switching of grid connected elements such as load, capacitors, reactor banks and generators of power producing units connected to the grid.
Use of passive filters for filtering undesired harmonics is possible. However, passive filters are expensive and require relatively large space.
Harmonic distortion may particularly be generated by wind turbine generators, solar power generators, hydro electric generators or generators or other power producing units.
Since harmonic grid distortion is a problem there is a need for a method for reducing harmonic distortion in connection with grid connected power producing units.